#include <stdio.h> 
#include <string.h> 
int main()
{
	char a[101], s[101];
	int i, len, mid, t, top;
	top = 0;
	gets(a);
	len = strlen(a);
	mid = len / 2 - 1;
	
	for (i = 0; i <= mid; i++)
	{
		top++;
		s[top] = a[i];
	}
	if (len % 2 == 0)
		t = mid + 1;
	else
		t = mid + 2;
	for (i = t; i < len; i++)
	{
		if (a[i] != s[top])
			break;
		top--;
	}
	if (top == 0)
		printf("yes");
	else
		printf("no");

	
	getchar(); getchar();
	return 0;
}